At the electro-music 2009 festival I was one of two people who shared the laptop battle victory. I saw all of the performances and they were all equally good, so I don't know how the judges chose but anyway what I did was attach a USB three-axis accelerometer board to my hand and make music by waving my hand around.

This was so well received that on the way home I imagineered a really fun thing to do: Musical Tai Chi. I'm going to start working on little circuit boards that create sound when they are moved around, causing an audio response to dance or motion such as Tai Chi. Being very overweight, I think that the light exercise of Tai Chi is just what I need to help me slim down a bit, plus I'd like to get familiar enough with it that I can hold Musical Tai Chi classes at festivals like EM10 and so on.

For now, I will just work with my existing tethered computer set up, but what I imagineered is a small, low-cost hand-mounted board that creates audio in response to Tai Chi motions and then broadcasts it on the AM radio band. Then people could put a board on each hand and an AM radio would pick up everyone's signal and send it to the PA system. As we all do Tai Chi, there would result a chorus of tones to the venue, which would be a lot of fun. Some additional details I've thought about are as follows:

o The audio provides feedback of correct Tai Chi motion so that if you don't move properly you can hear it.

o The boards are battery powered with on/off switch and LED indicator.

o Cost should be around $25 or so to enable most folks to go home with one or two of them.

o Use a 3-axis accelerometer chip from Analog Devices that outputs three analog voltages for X, Y, and Z.

o Provide for left/right panning in response to motion.

o Provide for frequency shifting in response to motion.

o Maybe do echo/reverb as well.

o Keep the board very simple and small.

o If you don't move smoothly and fluidly, you can hear it easily. This includes warbling if your hand shakes and tonal shift if you move unevenly.

o Other stuff I can't remember at the moment.

I'm open to all variety of suggestions and design ideas, so please feel free to put your thinking cap on for this one, thanks.

Yes for sure bluetooth is a good thing here. I plan to cut the wires with a bluetooth networking product sometime, but it requires battery usb power and an adapter from mini usb to usb or somesuch arrangement. I'll work with the cabled board for now and prototype the idea by expanding the laptop battle program in such a way that it models an easily implementable circuit. Then later come other solutions.

I'm astounded by your productivity Les. Of cause Tai Chi would not be the only field where this would come in handy.

These would be gestural musical instruments in their own right. Or indeed controllers as Wmonk suggested. Adapted Wii or Nunchuck controllers through an Arduinoboard have a sluggish response. An XYZ sensor especially dedicated to soundcontrol might improve this. Great idea!

Cost should be around $25 or so to enable most folks to go home with one or two of them...

I bought a Nunchuck for 19,50 euros, so yours could be a steal for $25. I'd be amazed if you could add echo/reverb for that price, that doesn't sound that simple to me.

Most simple AM radio's are mono. As a "cheap and cheerful" portable musical instrument I'd skip the panning.
For theremin like use volume would be indispensible. Pitch is, obviously. Then you could have the remaining parameter dedicated to timbre, like with a filter or waveshaper of sorts.

Mind overflows with possible uses now. Have a couple of them dangling in a door opening like these insect barrier curtains if you know what I mean. Put them in a ball to play throw and catch. Etc. etc. etc.... Fun!

Yes Mathe, the possibilites really do seem endless. I think you're right about not adding reverb and stuff. Perhaps all that is needed is an oscillator who's frequency is a function of the acceleration value. If you move your hand quickly, the frequency jumps up. If your hand is shaky, the frequency warbles. So you try to have smooth, slow, fluid motions which are the goal in Tai Chi.

The trouble is, the device reports X, Y, and Z as analog voltages so they must be squared, summed, and square rooted to get an acceleration vector. This is too much for a simple little board.

Perhaps the answer is to have three separate oscillators, one for each axis, all running at say 1MHz which is the middle of the AM band.

If you move your hand quickly, the frequency jumps up. If your hand is shaky, the frequency warbles. So you try to have smooth, slow, fluid motions which are the goal in Tai Chi.

Yeah, to keep a note going you would have to keep moving. That's one way of playing it , but a button to engage a sample and hold to hold your gestured note would come in handy for musical use i would imagine.

With a theremin hand position would determine the outcome, not acceleration. So with the acceleration sensor you'd want to convert to speed, then multiply speed by time to know where you are. This is a totally other implementation of your idea I realise, and at this point my nunchuck controller project came to a halt. would this be possible? Maybe you already mentioned this, I'm not sure.
I suck at mathematics, I got this wierd thing, as a reflex,my mind goes blank when calculations pop up.

Mathe, I have looked into doing this and it's really tough to do. You see, to track position by integrating the X, Y, and Z axes you would have to hold the device perfectly level and not rotate it. Also the thing is constantly measuring gravity as well as G forces, so that's another factor.

To properly track motion you need a 6-axis sensor that reports the pitch, roll, and yaw angles as well as the X, Y, and Z values. Then you have to do the same math that's required to dock the Space Shuttle! I looked up the math in the past, I forget what it's called - Euler equations IIRC - and it's tough!

What we need to look into is some simple, elegant solution that would be really small and cheap. Also the part is miniature so it will be necessary to have the boards assembled by the board house, so we might as well make it all surface mount parts.

Ok Inventor, You have me very excited about these devices, I am a professional juggler/performer, I do shows, perform on stilts.... ( as well as musician... ) My mind boggles with possibillities.I also have a venture with a creative partner who is a Chi Gong teacher/martial artist. I perform mainly solo at many festivals each year, I am sure we can help each other some way with this.

1. would there be any restrictions on speed of movement?
2. lets put them not only on the hands but lots of other body parts also.
3. they would become part of a costume
4. ooh lets put versions of them in the props I juggle
5. how do they relate to each other when at different distances?

Could be a beautiful cacophony (plenty of possiblities for comedic application also)
Aah I could go on...

1. would there be any restrictions on speed of movement?
2. lets put them not only on the hands but lots of other body parts also.
3. they would become part of a costume
4. ooh lets put versions of them in the props I juggle
5. how do they relate to each other when at different distances?

Thanks Cap for your thoughtful reply. Here are your answers:

1. The sensors max out at +/- 3G of acceleration.
2. Yes, can do
3. Yes, that is done with these types of things.
4. They are wired, but there is a wireless alternative.
5. They report acceleration, independently.

Cap, to do position tracking with these things, you need a 6-axis sensor and something called "Euler Equations", which is basically the math they use to dock the space shuttle. So yeah, can be done. There are other technologies if you have the means to apply them.

To do position tracking with these things, you need a 6-axis sensor and something called "Euler Equations", which is basically the math they use to dock the space shuttle. So yeah, can be done. There are other technologies if you have the means to apply them.

"Can be done." " If you have the means to apply them."

Translation: "Only Nasa , Pentagoon or Criminal Intelligence Agency can afford this technology." Or so it seemed only just half a year ago. Now this prebuilt airmouse: http://www.engadget.com/2007/07/12/logitechs-mx-air-mouse-a-witches-brew-of-lasers-mems-and-rf/ ships in the US and Europe for $150 sometime in August.
Your easiest option is to wait till then and buy it to try out.
Unless you're whizz and can develope your own from scratch, peripheral electronics, wireless contact to the processor, write drivers maybe, convert the inputs to OSC or MIDI, route this to your sound generator software of choice, etc. etc. etc.

Captain Quirk wrote:

1. would there be any restrictions on speed of movement?

Besides the 3G limit there's another bottleneck, that is "polling rate" of the sensor, baudrate / data transmission speed and processing speed.
Intuitively I'd expect it to be too low for incorporation in a juggling object. The Space Shuttle wasn't being smacked into a Space Station with the speed you'd hurl some object into the air. I see potential for hand(held) gestures. But I see juggler's (erm..) 'Clubs" ? tumbling, and I guess ball are not having a straight movement up, but also a spin. Greatly complicating data processing. Then, a juggler would juggle three objects at least to be taken serious? Computers would expect just one of these Air Mouse things to be used, so you'd need some merging or multiplexing utility (wich is bound to be written by someone within half a year after those AirMice are available).

Don't let my obvious sceptisism put you off though, I'm as eager to see these kind of things working as you are.

interesting. i used the i-cube a number of times in performances with light sensors but i did not like all those wires. so bluetooth is an interesting option. also, you can use 2 camera to midi(max/dsp).
howard captured this vid in london of me during a performance:
http://electro-music.com/avis/roland_kuit-1.avi
it is not taj chi, but it will give you an idea:)_________________Roland Kuit
----------------------------
composer|research|synthesis|sound design|lecturer
http://rolandkuit.com/

Folks, this renewed interest in the Tai Chi thingie got me thinking about em10 and what i'm going to do for the laptop battle. So i coded up a simple oscillator program in ChucK that responds to waving hand motions. It makes computery beeping sounds when moved quickly, and gentle sweeping tones when moved slowly. This works for Tai Chi because your objective is to move fluidly i guess. It also may serve as part of a performance setup. Here is the ChucK program:

Now I think of it... a smartphone is ideal for this (iPhone, Android). They have bluetooth, x- y and z axis sensors, compass and a touch screen. When sending OSC signals with bluetooth to chuck, you have a great performance instrument! _________________Weblog!

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